Primary cultures of non-replicating parenchymal liver cells in sterile monolayers on collagen films are studied in terms of induction of spcific enzymes and active transport systems in response to hormones (glucocorticoids, insulin, glucagon, catecholamines) added singly, in combination, or sequentially. Responses are compared with those obtained with 4 different lines of Morris hepatomas maintained in serial cell cultures. The properties of the primary liver cultures are related to the condition of the donor rat at the time of death in relation to time of day on a controlled feeding and lighting regimen. BIBLIOGRAPHIC REFERENCES: Kletzien, R.F., Pariza, M.W., Becker, J. E., Potter, V.R., and Butcher, F.R. Induction of Amino Acid Transport in Primary Cultures of Adult Rat Liver Parenchymal Cells by Insulin. The Journal of Biological Chemistry, 251: 3014-3020 (1976). Pariza, M. W., Yanagi, S., Gurr, J.A., Bushnell, D.E., Morris, H.P., and Potter, V.R. Ornithine Decarboxylase Activity and DNA Synthesis in Morris Hepatomas 5123C and 7800. Live Sciences, 18: 39-48 (1976).